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What Are The Effects Of Lowering Blood Pressure Targets?

In 2017, the American Heart Association (AHA) lowered the threshold for what constitutes hypertension. However, what is the impact of this, and is implementing these new guidelines cost effective? Two new studies set out to investigate.

According to the AHA, around 103 million adults in the United States have high blood pressure. They expect that this number will continue to rise.

Meanwhile, the Centers for Disease Control and Prevention (CDC) estimate that around 1,100 people die of a condition related to hypertension each day, including heart disease and stroke. These are some of the leading causes of death in the U.S.

The healthcare costs of hypertension are not negligible, either. The CDC suggest that hypertension results in almost $50 billion per year in costs, including the price of medications and missed days of work.

What are some of the measures that people with high blood pressure and healthcare professionals can take to prevent these adverse outcomes and increase lifespan? In 2017, the AHA recommended lowering blood pressure thresholds and treating people at risk more intensively.

Now, two new studies — both of which featured at the AHA's Scientific Sessions 2019, which takes place in Philadelphia, PA — have investigated the costs and benefits of treating hypertension more intensively, and of tailoring treatment according to degrees of cardiovascular risk.

Better blood pressure control lengthens life

Dr. Muthiah Vaduganathan, an instructor of medicine at Harvard Medical School and an associate physician at Brigham and Women's Hospital — both in Boston, MA — is the lead author of the first study.

Dr. Vaduganathan and team used data from the well-known Systolic Blood Pressure Intervention Trial (SPRINT).

The SPRINT examined the effects of lowering systolic blood pressure readings to a target of 120 milligrams of mercury (mm Hg) instead of the usual 140 mm Hg.

The trial followed 9,361 participants, all of whom were over the age of 50 and at high cardiovascular risk. The SPRINT followed them for 6 years and concluded that lowering blood pressure targets reduced the risk of cardiovascular problems — such as heart attack, stroke, heart failure, and cardiovascular death — by 25%.

The participants were at high risk of heart disease if they had had a cardiovascular disease that was not stroke, scored highly on the 10 year cardiovascular risk score, had chronic kidney disease, or were older than 75.

For the new study, the researchers analyzed the data to project the lifespans of the participants who underwent intensive hypertension treatment to lower blood pressure to a target of 120 mm Hg. They compared these projected lifespans with those of participants who received the standard treatment that aimed for a blood pressure of lower than 140 mm Hg.

The study revealed that intensive blood pressure treatment increased lifespan by 4–9%, compared with standard care.

"In contrast with the oldest patients, middle-aged patients had the greater absolute benefit because they start with a longer expected lifespan and can receive the intensive treatment over a longer period of time," explains Dr. Vaduganathan.

Dr. Mitchell S. V. Elkind — the AHA president-elect and chair of the Advisory Committee of the American Stroke Association — comments on the results. He says, "This analysis of the [SPRINT] suggests that [there are] additional years of life that can be added by more aggressive control of blood pressure."

He adds, "When you tell people that lowering their blood pressure is going to reduce their chance of having a stroke or a heart attack by 25%, which is what [the SPRINT] showed," the question that naturally ensues is "what does that number mean, in real terms?"

"This analysis suggests that for a man who is 50 years old, lowering blood pressure to [the lower] targets could extend your lifespan by 3 years, on average."

Dr. Mitchell S. V. Elkind

"High blood pressure has been implicated as one of the reasons for stalled progress in reducing heart disease-related deaths in the United States," Dr. Vaduganathan says. "These data reinforce that tighter blood pressure control, especially when started earlier in life, may meaningfully prolong lifespan."

New guidelines to treat an extra 5.2 million

The second study examined the best way to implement the new blood pressure guidelines issued by the American College of Cardiology (ACC) and the AHA.

These new guidelines lowered blood pressure thresholds to define hypertension as anything from 130/80 mm Hg to 140/90 mm Hg.

The new guidelines also recommend medication treatment for people with a blood pressure reading of 130/80 mm Hg to 139/89 mm Hg if they have a history of heart attack or stroke, or if they have a high 10 year risk of experiencing such an event.

Joanne M. Penko — a research data analyst at the University of California, San Francisco — is the lead author of this second study.

To assess the cost effectiveness of implementing the new guidelines, Penko and colleagues looked at healthcare costs and quality-adjusted life years (QUALY). They used the Cardiovascular Disease Policy Model, a well-known computer simulation model, to estimate healthcare costs over a 10 year period.

Compared with the 2003 guidelines, the analysis revealed, the "2017 ACC/AHA guidelines would treat 5.2 million more adults 35–84 years of age, intensify treatment in another 11.7 million, and prevent about 257,000 [cardiovascular] events over 10 years."

Intensifying treatment pays off over a 10 year period for men aged 65–84 and women aged 75–84 who already have cardiovascular disease. For others, however, the costs outweigh the benefits.

Furthermore, treating people at high cardiovascular risk who had not had cardiovascular disease would only be intermediately cost effective for adults whose blood pressure readings are 140/90 mm Hg or higher at baseline. It would not be cost effective at all for those whose blood pressure readings are 130/80 mm Hg to 139/89 mmHg.

"Previous studies have shown that compared with no treatment, treating high blood pressure according to the 2003 Seventh Report is cost effective over 10 years," Penko says. "We were surprised to learn in our study that wasn't the case for all patients indicated for medication treatment in the 2017 guidelines."

"The study's findings suggest an incremental approach to implementing the 2017 ACC/AHA hypertension guidelines, first focusing limited resources on treating the oldest, highest-risk adults to intensive blood pressure goals."

Joanne M. Penko

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